Add findNearestCommonDominator() for PostDominators.

Add a missing interface to be able to call findNearestCommonDominator
for a PostDominanceTree. The function itself is already implemented in
DominatorTreeBase. The interface however was only added to the
DominatorTree class, but not the PostDominatorClass.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97915 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/PostDominators.h

@@ -69,6 +69,10 @@ struct PostDominatorTree : public FunctionPass {
     return DT->properlyDominates(A, B);
   }
 
+  inline BasicBlock *findNearestCommonDominator(BasicBlock *A, BasicBlock *B) {
+    return DT->findNearestCommonDominator(A, B);
+  }
+
   virtual void releaseMemory() {
     DT->releaseMemory();
   }